1. Field of the Invention
The present invention relates to an apparatus and a method of removing an offset of a PLL (Phase Locked Loop) circuit, and more particularly, to an apparatus and a method of removing an offset of a PLL circuit, used in a disc drive when data playback is performed.
2. Description of the Related Art
A PLL circuit of a disc drive generates a reference clock signal when performing data playback. Therefore, the PLL circuit of the disc drive must work in synchronization with a playback RF signal. However, before the PLL circuit of the disc drive synchronizes with the playback RF signal, an offset of the PLL circuit must be removed in order to increase accuracy of the reference clock signal output from the PLL circuit.
In a conventional method, the offset of the PLL circuit is removed using an RF signal generated by a test disc. Therefore, it takes a long time to remove the offset of the PLL circuit since the test disc is first inserted in the disc drive and an RF signal is obtained from the test disc.
Also, since the same test disc is used repeatedly in order to remove the offset of the PLL circuit, the test disc can become damaged. When the damaged test disc is used to remove the offset of the PLL circuit, an offset removal procedure of the PLL circuit may fail. If the offset removal procedure of the PLL circuit fails, playback data quality deteriorates since errors are contained in the generated clock signal.